Insulator



March 10, 1931. SCHERMERHQRN 1,795,652

INSUEMXZ'QR Filed July l, 192% Harmon L. Schermerhorn,

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His Attorney.

Patented Mar. 10, 1931 UNITED STATES PATENT orrics HARMON L. SCHERMERHORN, F SCOTIA, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC T 1' COMPANY, A CORPORATION OF NEW YORK INSULATOR Application filed July 1, 1926.

My invention relates to insulators, more particularly to insulators used in securing the segments of commutators in electrical apparatus, and has for its object the provision of a simple, reliable and inexpensive insulator of this type.

In the manufacture of commutators it is customary to provide projections, forming dove-tails, at the ends of the segments, the segments being secured together by means of clamping rings which en 'age with the projections. Suitable insulation is provided between the segments themselves and also between the clamping rings and the segments. My invention relates more specifically to insulators for use between the clamping rings and the segments. For convenience in the assembly of the commutator these insulators have heretofore been constructed as unitary, cylindrical or annular members which fit over the end rings. One of these formed insulators is used with each clamping ring at the opposite ends of the commutator.

In carrying out my invention I form the insulator from strips of insulating material which are arranged in layers and extend obliquely with respect to the axis of the insulator. The strips preferably are secured together by means of an adhesive, the insulator being shaped and the strips compacted in a suitable mold.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a perspective view of a formed insulator embodying my invention; 2 is an outline view of an insulating strip from which the insulater is made; while Fig. 3 a fragmentary sectional view showing a typical installation of an insulator of this type.

Referring to the drawing, in carrying out my invention in one form, I construct the cylindrical insulator 10 from a plurality of strips 11, which extend obliquely with respect to the longitudinal axis of the cylinder, i. e.,

Serial No. 119,968.

diagonally across said insulator. These strips are made of a suitable insulating material, preferably mica. At one end the outer cylindrical portion 10 of the insulator is in elfectcrimped or bent over inward to form a reentrant rim portion 12 which extends back inside of the outer cylindrical portion at an acute angle therewith. This rim portion 12 terminates in an internal flange 13 which is bent back at an acute angle with the portion 12.

The strips of insulation 11 are shaped in such manner as to provide for the portions 12 and 13 at one end, this shape being indicated in a general way in Fig. 2. It will be observed that the strip is roughly a parallelogram having its parallel ends extending obliquely with respect to the sides, but with a slightly tapered portion 11 at one end, this tapered portion being bent over to form the portions 12 and 13. As shown, the tapered portion 11 is formed by beveling one side only of the strip although if desired both sides may be beveled. The form shown gives greater economy in material when the strips are out. At the end of the tapered portion 11 a short length 11 parallel with the opposite side is formed in the beveled side, this end portion of the strip forming the flange 13 of the insulator. The final shape of the strips as formed in the completed insulator will be apparent from an examination of Fig. '1.

In the assembly or" the insulator, the strips are placed in their oblique positions in a suitable mold in a plurality of layers, the

thickness of the completed insulator comprising the combined thicknesses of a number of strips. The strips in each layer are placed side by side around the periphery of the insulator, the strips of each successive layer overlapping the abutting edges of the strips of the preceding layer. After being arranged in this manner in the mold, the strips are pressed together and shaped. in the form shown in Fig. 1, a suitable adhesive being used to secure the strips together. For example, the strips may be coated with shellac and shaped and compacted in a heated mold whereby the shellac is softened and a unitary structure of satisfactory mechanical strength formed. 1 p

A typical application of my insulator is shown in Fig. 3 in which the commutator seg ments 16' are secured together between clamping rings 17 and 18, the clamping rings being tapered in cross section so as to engagewith the dove-tail projections 19 and20 on the commutator'segments. As shown the clamping ring 18 is secured on one end of a cylindrical supporting member 21-which extends through the commutator.

The ring 17 is slipped on" nating in an inner flange forming an acute angle with said rim portion, said insulator being formed of strips of insulating material extending diagonally across said insulator portions in a plurality of layers, the strips 7 in each layer being in abutting relation and the supporting member 21 and secured by means of a nut 22 which is screwed on the threaded end of the support 21. ;-The nut 22 is seated securely against the ring 21 so as to pull the two rings toward each other and, clamp them securely on the commutator segments. It will be observed that the insula tors 1O are placed over the clamping rings, the rim portion 12 lying between the oblique V edge of the clamping ring and the dove-tail projection of the commutator segment.

The insulators constructed in accordance with my invention have great dielectric andmechanical strength. The arrangement of the strips obliquely playsan important part in giving the insulator mechanical strength, since it will be observed that the overlapping of the strips is more effective when the strips are placed in this manner. Furthermore the insulator is inexpensive to manufacture since the strips may be originally cut in such shape as to form the inwardly turned portions 12 and 1.3 so that the insulator maybe formed in one operation. Economy in the use of insulating material is obtained since there need be but little Waste of material in the cutting of the strips. in structure and uniform in thickness. Another advantage is that the commutator bars or se 'ments cross the abutting edges of the strips obliquely. This avoids the possibility of the bars sinking at the joints and becoming loose which occurs,I have found, if the strips are placed parallel with the axis of the insulator.

lVhile I have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention the scope of which is set forth in the annexed claim.

' What I claim as new and desire to secure by Letters Patent of the United States, is

A molded insulator comprising a cylindrical portion and a reentrant rim portion termi- The insulator is also very'dense 

